This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Purpose of this study is to test whether prolonged oral antiviral therapy improves long term outcome of herpes simplex encephalitis [HSE] following standard IV antiviral treatment. Specific questions being looked at are: 1- Does long term oral valacyclovir improve outcomes in HSE? 2- How does the body absorb, metabolize, and eliminate high dose oral valacyclovir when used long term for HSE? 3- Is there a relationship between neurologic outcomes following HSE and the amount of Herpes Simplex virus in the Central Nervous System?